Sealants

ABSTRACT

A group of sealants are described which utilize a by-product of paint booth spray operations. Processed paint booth overspray particles are combined with various resins, curing agents to form the sealant compositions.

This Application is a continuation-in-part or U.S. application Ser. No.09/944,975 entitled “Sealants”, filed on Aug. 31, 2001, from whichpriority is claimed and the entire disclosure of which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates generally to resin-based sealing materialsfor use in closing gaps and holes in a variety of structuralenvironments.

BACKGROUND OF THE INVENTION

In the automotive industry it is often necessary to seal gaps and jointsin metal structures using an adhesive bead, plug or patch. For example,where a stamping and a structural beam meet a longitudinal gap mayarise. In addition, drainage holes, assembly access holes, fasteningholes and the like are often formed in automobile body structures andmust be subsequently closed. As will be appreciated by those skilled inthe art, if left unsealed these gaps and holes allow dust and fumes toenter the passenger compartment and create a source for water leakageand corrosion.

It is known that the cost of resins often exceeds that of othermaterials. Accordingly, significant research has been conducted toproduce resin-based sealants which take advantage of low-cost startingmaterials.

It is also known that when manufacturing plants spray automotive bodiesin paint spray booths, only 50-60% of the paint spray actually adheresto the surface being painted. Typically, that portion of the paint spraythat does not adhere (the “overspray”) is exhausted from the spray boothby means of a wet scrubber system. Of course, a wide variety of paintformulations are used in the industry. The resulting overspray, whichmay be a mixture of different paint formulations from multiple paintapplications, is generally treated in solution to detackify the paintparticles so they are non-sticky. Next, a process the paint particlesare flocculated so they can be collected. Heat is then applied to theresulting paint solids to drive off all of the volatiles and water. Oncethe paint solids are dried and sized, they have the consistency of apowder; the chemistry of these solids is very similar to the paint thatwas applied in the paint booth.

SUMMARY OF THE INVENTION

In one aspect the present invention provides resin-based materials foruse as sealants. The inventive sealant materials include as a keycomponent processed overspray from an automotive paint booth. Theprocessed paint booth overspray preferably comprises substantiallyfully-cured overspray resins in particulate form. In one aspect thepaint booth overspray is principally a substantially fully-cured acrylicmaterial. In another aspect, the paint booth overspray also includessubstantially fully-cured epoxy material. As used herein, “substantiallyfully-cured” shall mean the resins are substantially inert; that is, thepolymers do not undergo any significant further polymerization or crosslinking. In one aspect, the inventive compositions also include ablowing agent to produce an expandable material.

In another aspect the present invention provides a method of sealing agap with a resin-based sealant materials which include as a componentprocessed overspray from an automotive paint booth.

In still another aspect of the present invention, a method of making asealant material which contains processed overspray from an automotivepaint booth.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a photomicrograph of particles of processed paint boothoverspray used in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The compositions of the present invention are sealants for use infilling gaps between and in structural parts, such as small gaps at theinterface of two structural parts or holes. The inventive compositionsutilize processed paint booth overspray as one constituent. Processedpaint booth overspray is prepared in the conventional manner bycollecting paint overspray from a paint booth chamber. It will beappreciated that motor vehicle bodies receive a series of coatingsduring manufacture. When sprayed, these coatings are typically appliedin controlled chambers in which a wet-scrubber system collects thecoating overspray. One such application provides a primed surface on thevehicle body. It is believed, however, that the primers which are usedmay not be optimally suited for use in forming sealant compositions dueto the residual reactivity and chemical make-up of the primer overspray.At a later stage of the coating process, however, a layer of paint isapplied to the primed metal surface of the vehicle body. It is thispaint overspray which, once processed, is used as a component of thesealants of the present invention.

It is to be understood that the composition of paint booth overspray isdetermined by the composition of the paints used in the paint sprayprocess. Preferred paint booth overspray in the present inventioncontains from 1% to 100% by weight acrylic. More preferably, the paintbooth overspray preferred for use in the present invention isprincipally comprised of acrylics. In the most preferred embodiment ofthe present invention, the processed paint booth overspray particles arepreferably at least 50% by weight substantially fully-cured acrylicresins, i.e. substantially fully reacted acrylic polymers. That is, inthe most preferred embodiment, the acrylics of the processed paintoverspray lack any substantial content of unreacted functionalities. Theprocessed paint booth overspray may include lesser amounts (preferablylesser amounts) of various other paint resins such as epoxies and thelike and small amounts of cross-linking agents such as melamines. Aswith the acrylics, these additional resins are preferably substantiallyfully-cured, i.e., they should lack any substantial content of unreactedchemical functionalities. By assuring that the polymers of the processedpaint booth overspray are substantially unreactive, unwanted reactionsin the resin-based structural materials of the present invention areavoided.

Referring now to FIG. 1 of the drawings, the particles of substantiallyfully cured paint booth overspray particles used in the presentinvention are shown. The individual particles preferably have an averagesize of from about 50 and 200 microns (diameter) with particles rangingin size from about 10 microns to 400 microns (diameter). In terms ofmesh size the preferred substantially fully-cured paint booth oversprayused in the present invention is preferably about 120 mesh (U.S. meshstandard).

As stated above, the paint booth overspray is collected from the paintspray booth, typically by a wet-scrubber system. The paint overspray isthen treated with a detackifying agent to detackify the particles. Aflocculating agent is then applied to the solution which causes thepaint particles to aggregate whereupon they are collected. Thedetackified, flocculated paint overspray is then further processed bydrying, particlizing and sizing using conventional particle sizingtechniques such as sizing meshes and the like. Any unreacted resin andpolymer functionalities are preferably substantially fully reactedduring this drying process through use of heat in the drying operation.

A preferred substantially fully cured paint over spray composition foruse in the present invention is sold by Hayden International under thetrade name “DRYPURE II.” DRYPURE II is principally comprised ofsubstantially fully-reacted acrylics, with a minor amount ofsubstantially fully-cured epoxies and melamines.

In a preferred embodiment of the resin-based structural materials of thepresent materials, the substantially fully-cured processed paint boothoverspray particles form about 5% to about 75% percent by weight, andmore preferably from about 10% to about 50% and most preferably fromabout 20% to about 35% of the sealant composition.

In addition to the paint overspray particles, the preferred formulationsof the present invention contain from about 5% to about 75% and morepreferably from about 10% to about 60% resin by weight, from about 0% toabout 70% and more preferably from about 5% to about 30% by weightfiller, from about 0% to about 10% and more preferably from about 0% toabout 10% and more preferably from about 1% to about 10% by weightblowing agent, from about 0% to about 10% and more preferably from about1% to about 5% weight curing agent and from about 0% to about 10% andmore preferably from about 0.5% to about 2% weight accelerator.

Preferably, the resin component of the inventive sealant compositionsare a blend of resins, which may include one or more elastomers.Preferred thermoplastic resins useful in the present invention arepolyolefins, preferably copolymers and terpolymers containing ethylene,for example, ethylene vinyl acetate copolymers, ethylene ethyl acrylate,ethylene-maleic anhydride copolymers, ethylene-vinyl acetate-glycidalmethacrylate, ethylene acrylate-maleic anhydride, and ethylene-propylenecopolymers. Fully acromatic hydrocarbon resins such as Norosolen S105and Nevex 100 or Cumarone-indene resins such as Cumar R-012 may also beuseful. Copolymers of ethylene with butene, hexene or octene are alsopreferred. Also, certain block copolymers such as an styrene-butadieneblock copolymer may be suitable. Copolymers and terpolymers containingpolyvinyl chloride are also preferred for use herein. Preferredthermosetting resins for use in the present invention are epoxies,acrylates, and polyurethanes and combinations thereof. EPDM isparticularly preferred.

In one preferred embodiment, the resin component includes a polyolefinresin, preferably a combination of ethylene vinyl acetate copolymer(EVA) and one or more acrylic resins, such as ethylene methyl acrylate,ethylene ethyl acrylate and ethylene butyl acrylate. The preferred EVAhas from about 9 to about 40 percent by weight vinyl acetate and thepreferred ethylene methyl acrylate, ethylene ethyl acrylate and ethylenebutyl acrylate have from about 20 to about 40% methyl acrylate, ethylacrylate or butyl acrylate, respectively.

A cross-linking or curing agent is also preferably included in thesealant compositions to cross-link the polyolefin. Preferredcross-linking agents should provide a reasonable shelf life, but shouldalso be fully activated at the temperatures encountered in the curingenvironment such as automotive paint ovens. Suitable curing agentsuseful in the present invention are peroxy compounds such as1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane andn-butyl-4,4-bis(t-butylperoxyl) valerate and particularly preferred areVarox 130XL, Varox 230XL and Varox 231XL sold by R. T. VanderbiltCompany.

In the most preferred embodiment, the curing agent includes amultifunctional cross-linking monomer such as trimethylolpropanetrimethacrylate, pentaerythritol pentaacrylate, or trimethylolpropanetriacrylate to increase cross-linking density.

The use of an agent which produces expansion of the sealant compositionswhen it is heated, for example, in the automotive paint oven or thelike, provides a more uniform and reliable seal of access holes andgaps. Expansion may not be needed in all applications but will bebeneficial in many applications. Accordingly, in the preferredembodiment of the invention, the sealant compositions contain a blowingagent, preferably one which is thermally-activated, such asazodicarbonamide, para, para-oxybis(benzenesulfonyl-hydrazide) andpara-toluene sulfonyl semicarbazide. Preferred are Celogen OT andCelogen AZ. Preferably the blowing agent produces a volumetric expansionof the sealant composition from about 25% to about 1500% by volume ofits unexpanded volume. The preferred blowing agent is fully activated atabout 100 to about 165 C.°.

In addition to the above components, it is most preferred that thecomposition include from about 0.0 to about 1.5% and, more preferably,from about 0.3 to about 0.8% by weight sodium acetate (CH3COONa) as itstrihydrate (CH3COONa 3H20), also known as sodium acetate trihydrate.Preferably sodium acetate is provided as a blowing agent activator.

It will be appreciated that the processed paint booth oversprayfunctions principally as a filler. If additional fillers are need ordesired, the following materials are suitable for that purpose: calciumcarbonate, talc, clay, mica, and calcium sulfate.

In a number of applications, a tackifier component may also be includedin the present invention to provide adhesion and to enhance peelstrength. A number of tackifiers suitable for use herein will be knownby those skilled in the art. Preferred are partially aromatichydrocarbons such as “Escorez 2393” and “Staytac 100.” Most preferred isSuper Nevtac 99 or Cumar R-13 (Coumarone-Indene resin) available fromthe Neville Chemical Company.

A number of additives or co-agents may also be included in the sealantcompositions such as antioxidants, antiozonants, ultraviolet absorbers,antistatic agents, colorants, coupling agents, curing agents, flameretardants, blowing agents, heat stabilizers, impact modifiers,lubricants, plasticizers, preservatives, processing aids such as oilsand stabilizers and combinations thereof.

One preferred formulation of the inventive sealants is set forth belowin Table I:

TABLE I Component Preferred Range (% by weight) Base Resin (copolymersand 10 to 50 polymers Cross-linking Agent 1 to 3 Tackifier Resin  5 to20 Paint Booth Overspray 10 to 40 Other Fillers  0 to 30 Processing Aids 5 to 20 Co-agents  1 to 10

TABLE II Component Preferred Range % by Weight EPDM (low molecularweight; 20-30 very high ethylene content; medium diene level) High flowcopolymer of ethylene and 3-6 vinyl acetate Linear polyethylene  5-10homopolymer Cure accelerator 0.1-0.3 Epoxy resin 1-3 Tackifier  8-12Dripure 2 25 Sodium acetate  .2-1.0 Zinc oxide 1-2 Organic accelerator .4-1.0 Sulfur  .4-1.0 Zinc dibutyl dithiocarbamate  .4-1.0 Urea-basedaccelerator 0.1-0.5 activator Azo blowing agent  7-10 Paraffinicprocessing oil  6-10 Isobutylene/butene copolymer 4-8

The inventive compositions are formed by admixing the above componentsusing standard mixers and the like. In other words, the ingredients arecombined and mixed to form the composition which can then be molded,extruded and the like to the desired shape.

In the method of the invention the sealant compositions are prepared,then preferably formed to near-net shape, and placed in the desiredlocation for filling a gap or hole. The composition is then heated tothermally activate the blowing agent, whereupon the sealant expands toconform to adjacent surfaces and adhering thereto.

While particular embodiments of this invention are shown and describedherein, it will be understood, of course, that the invention is not tobe limited thereto since many modifications may be made, particularly bythose skilled in this art, in light of this disclosure. It iscontemplated, therefore, by the appended claims, to cover any suchmodifications as fall within the true spirit and scope of thisinvention.

What is claimed is:
 1. A sealant composition, in admixture comprising: aresin, paint booth paint overspray particles; a curing agent; and ablowing agent.
 2. The sealant composition recited in claim 1, whereinsaid resin comprises from about 5 to about 75% by weight of said sealantcomposition.
 3. The sealant composition recited in claim 1, wherein saidpaint booth paint overspray particles comprise from about 5 to about 75%by weight of said sealant composition.
 4. The sealant compositionrecited in claim 1, wherein said curing agent comprises from about 1 toabout 5% by weight of said sealant composition.
 5. The sealantcomposition recited in claim 1, wherein said resin is selected from thegroup consisting of ethylene vinyl acetate, ethylene ethyl acrylate,ethylene-maleic anhydride, ethylene-vinyl acetate-glycidal methacrylate,ethylene acrylate-maleic anhydride, ethylene-propylene copolymers andterpolymers, styrene-butadiene block copolymers, polyurethanes, epoxiesand combinations thereof.
 6. The sealant composition recited in claim 1,wherein said curing agent is peroxide.
 7. The sealant compositionrecited in claim 1, wherein said blowing agent is thermally activated.8. The sealant composition recited in claim 1, further including afiller selected from the group consisting of calcium carbonate, talc,clay, mica, calcium sulfate, and combinations thereof.
 9. The sealantcomposition recited in claim 1, wherein said blowing agent is thermallysubstantially fully activated at between 100 to 165 degrees C.
 10. Asealant composition comprising: from about 5% to about 75% resins; fromabout 5% to about 75% by weight substantially fully cured processespaint booth paint overspray; from about 1% to about 5% by weight curingagent; and from about 1% to about 10% by weight blowing agent.
 11. Thesealant composition recited in claim 10, wherein said resin is selectedfrom the group consisting of ethylene vinyl acetate, ethylene ethylacrylate, ethylene-maleic anhydride, ethylene-vinyl acetate-glycidalmethacrylate, ethylene acrylate-maleic anhydride, ethylene-propylenecopolymers and terpolymers, styrene-butadiene block copolymers,polyurethanes, epoxies and combinations thereof.
 12. The sealantcomposition recited in claim 11, further including a filler selectedfrom the group consisting of calcium carbonate, talc, clay, mica,calcium sulfate, and combinations thereof.
 13. A method of making asealant composition comprising the steps of combining the followingcomponents into a mixture: resin, paint booth paint overspray particles;a curing agent; and a blowing agent.
 14. A method of filling a gap orhole, comprising the steps forming a sealant which includes a resin,paint booth paint overspray particles; a curing agent; and a blowingagent; applying said sealant to the surfaces surrounding said gap orhole; heating said sealant to expand the sealant and adhere the sealantto said surfaces.
 15. The sealant composition recited in claim 1,further including a blowing agent activator.
 16. The sealant compositionrecited in claim 15, wherein said blowing agent activator is sodiumacetate.
 17. The sealant composition recited in claim 1, furthercomprising sodium acetate.